Phase boundary and facet engineering

1. Phase boundary engineering in Co₂P–CoP nanoparticles for oxygen evolution electrocatalysis

Beyond point defects, the boundary between two different crystal phases within a single nanoparticle offers another fundamental lever for catalyst design atoms at these boundaries have unique electronic structures and coordination environments that can significantly enhance catalytic performance. Cobalt phosphide can adopt both Co₂P and CoP crystal phases, and by engineering branched nanoparticles that contain a controlled phase boundary between the two, we showed that the unique coordination environment at this interface enhances cobalt oxidation and drives substantially improved OER activity a clean energy solution built on precise atomic-scale control of nanoparticle structure (Figure 1).

In this project, you will synthesize branched cobalt phosphide nanoparticles with controlled Co₂P–CoP phase boundaries, and investigate how the position, density and chemistry of these boundaries govern OER activity and stability. This work combines synthetic nanoparticle chemistry with advanced electron microscopy and electrocatalytic testing to build a fundamental understanding of how internal crystal structure controls catalytic performance for hydrogen production and sustainable energy storage. You'll gain hands-on experience in nanoparticle synthesis, electron microscopy, and electrocatalytic testing, core skills for a career in clean energy, materials chemistry, or nanotechnology research in industry or academia. This project is well suited to PhD students and undergraduate (Honours/summer scholarship).

Figure 1. Electron microscopic images and elemental maps of the cobalt phosphide branched nanoparticles showing the phase boundary, the Co₂P–CoP phase boundaries are the most active for OER compare to have only Co₂P and CoP.

2. Iridium nanocrystals enriched with defects and atomic steps for oxygen evolution electrocatalysis

The presence of defects in a catalyst can significantly improve its activity and stability, since defects influence how reactants, intermediates and products bind to the catalyst surface. Controlling defects in nanocrystal catalysts is synthetically challenging. We developed a synthesis that controls the growth of iridium nanocrystals, tuning both structural and surface defects ranging from single crystals just a few nanometres across, to twinned nanoparticles, to multiply twinned crystallites with a high density of atomic steps. This defect engineering strategy reveals how atomic steps and twin boundaries enhance the oxygen evolution reaction (OER), producing an iridium catalyst that combines high activity with excellent long-term stability a rare combination for one of the most important, but scarce and expensive, catalysts for green hydrogen production via water electrolysis. (Figure 2)

In this project, you will synthesise iridium nanocrystals with controlled structural and surface defects, from single crystals to twinned and multiply twinned particles rich in atomic steps and investigate how these defects govern OER activity and stability. This work combines nanoparticle synthesis with advanced electron microscopy and electrocatalytic testing to build a fundamental understanding of how atomic-scale defects control catalytic performance, helping to minimise the amount of scarce, expensive Ir needed for high-performance water electrolysers. You'll gain hands-on experience in nanoparticle synthesis, electron microscopy, and electrocatalytic testing, core skills for pursue a career in industry or academia. This project is well suited to PhD students with an interest in materials chemistry, nanotechnology, and clean energy research.

Figure 2. High-resolution transmission electron microscopy images activity, and long-term stability data of iridium nanocrystals showing twin boundaries and atomic steps, high-energy defect sites that enhance the catalytic properties of iridium nanoparticles for efficient water electrolysis.

References

1. Ramadhan, Z. R.; Cheong, S.; Saha, S.; Li, Q.; Zheng, X.; Somerville, S. V.; Poerwoprajitno, A. R.; Kumar, P. V.; Dai, L.; Gooding, J. J.; Tilley, R. D. Phase Boundary Engineering of Co2P–CoP Branched Nanoparticles Enhances Cobalt Oxidation for Oxygen Evolution Electrocatalysis. Adv. Mater. 2026, e23118.
2. Ikram, F.; Cheong, S.; Persson, I.; Ramadhan, Z. R.; Poerwoprajitno, A. R.; Gooding, J. J.; Tilley, R. D. Iridium Nanocrystals Enriched with Defects and Atomic Steps to Enhance Oxygen Evolution Reaction Performance. J. Am. Chem. Soc. 2025, 147 (13), 10784–10790.